The present invention relates to a chemical adsorption material to be chemically adsorbed on a surface of a substrate to form a thin film thereon and to a producing method thereof. More particularly, the present invention relates to a chemical adsorption material used mainly as liquid crystal alignment film coating material for forming a thin film and to a producing method thereof. Also, the present invention relates to an organic thin film formed by use of the thin film forming chemical adsorption material and to a producing method thereof. Further, the present invention relates to a liquid crystal alignment film and to a producing method thereof. Furthermore, the present invention relate to a liquid crystal display using the same and to a producing method thereof and, further particularly, to a liquid crystal alignment film for use in a plane display panel using liquid crystals to display television (TV) picture, computer picture and the like, to a producing method thereof, and to a liquid crystal display device using it.
In recent years, liquid crystal elements come into wide use rapidly as means for miniaturization of information technology equipment. A liquid crystal alignment film which is the critical component of the liquid crystal elements is subjected to a rubbing process which can be cited as a typical alignment film treatment process. However, the rubbing process has difficulties of deterioration of display quality caused by generation of fine dusts and rubbing lines and others. To avoid these difficulties, rubbingless alignment film treatments, such as an optical alignment film treatment, are now under study.
Known optical alignment film treatments include the process that an alignment film made of polymer, such as polyimide or polyvinyl alcohol, is irradiated with polarized ultraviolet light for alignment film treatment. Another approach was also reported (by Japanese Patent Application No. Hei 8-224,219), in which the optical alignment film treatment is given to the optical alignment film comprising chemical adsorption monomolecular film, as well as to that of polymer such as polyimide. The optical alignment film treatment is performed under the alignment mechanism that admolecules of the film are irradiated with polarized light so as to be re-aligned, so that the liquid crystal molecules are aligned along the polarization direction.
In the case of the alignment film comprising polymer, it has the molecular structure that polymers are complicated densely and irregularly, except its surface part. Because of this, only a part of a surface of the film from which tip portions of the polymer projects out can contribute to the alignment of the liquid crystal molecules. In addition to this, because of uncertainty of the alignment orientation of the side chain, the functional group contributive to the alignment is not always exposed on the surface. Consequently, the part thereof contributive to the alignment of the liquid crystal molecules is obviously smaller in density than that of the monomolecular film, thus suffering the disadvantage that it is difficult to make an adequate control of alignment of the liquid crystals. Also, since the alignment film comprising polymer has large thickness and thus insulative property, it has the problem that transmission of light and electric field to drive the liquid crystal molecules are hindered.
In contrast to this, in the case of the alignment film comprising chemical adsorption monomolecular film, since the functional group contributive to the alignment of the liquid crystal molecules is fully exposed on the surface of the film, adequate control of alignment of the liquid crystals can be obtained. In addition to this, the alignment film of chemical adsorption monomolecular film is in a monomolecular layer form and thus has small thickness, as compared with the alignment film of polymer. Also, since it is chemically adsorbed on the surface of the substrate, it also has excellent adhesion property.
Thus, the conventional alignment film comprising polymer has the problems that adequate control of alignment cannot be obtained and that it has large thickness and thus insulative property. In view of the problems above, there has been developed and provided an alignment film comprising chemical adsorption monomolecular film.
The alignment film comprising chemical adsorption monomolecular film was rather useful for solving the disadvantages mentioned above. However, the admolecules forming the film are merely aligned and arrayed along the polarization direction, so that when the film is heated to high temperature, the alignment stability falls disadvantageously. Consequently, the development is being desired of a useful alignment film of monomolecular film form that is further excellent in thermal stability of alignment.
Incidentally, the conventional liquid crystal display has the structure wherein a pair of substrates, which have transparent electrodes arranged in a matrix form and liquid crystal alignment films formed on the transparent films, are arranged to confront each other, with a given gap therebetween with their liquid crystal alignment films facing inwards, and liquid crystal is sealed in the gap. Now, taking a color liquid crystal display as an example, a typical producing method will be explained below. A polymer membrane is formed on each of a first glass substrate on which pixel electrodes and thin-film transistor (TFT) array are formed and a second glass substrate on which a number of color filters of red, blue and green are formed and common transparent electrodes are further formed thereon. Then, these polymer-coated surfaces of the substrates are subjected to the rubbing to provide alignment characteristic of liquid crystal. Then, the substrates are so arranged that their coated surfaces can face inward and confront each other in the state in which spacers are interposed therebetween and are adhesive bonded around the margins thereof to form an empty cell (a panel structure).
Liquid crystal material, such as twisted nematic liquid crystal, is filled in and tightly sealed in the empty cell, to form the liquid crystal display element. Further, a polarizing plate is arranged on each outside surface of the element and also a backlight is disposed at the outside of the first glass substrate, to thereby produce the liquid crystal display as the optical display element.
In the liquid crystal display thus structured, the TFT of switching elements controls an interelectrode voltage to change the alignment of liquid crystals, so that the transmission of light is switched on and off in a pixel basis to display any desired image. Consequently, the alignment film that controls the alignment of the liquid crystals at the time of no applied voltage bears a significantly important part in exerting an influence directly on the display performance of the device.
Polyimide films have been widely used hitherto as a coating material of the liquid crystal alignment film, in terms of their excellence in affinity to liquid crystal, heat resistance, and adhesion to the substrate. In general, the polyimide film is produced by using either of the following two processes. One is that after liquid solution obtained by polyamic acid of precursor polymer of polyimide being dissolved in organic solvent such as xylene is rotationally applied on to the substrate, that substrate is baked to imidize the polyamic acid, so as to form the polyimide film. Another is that after liquid solution obtained by polyimide itself being dissolved in organic solvent such as DMF (N,N-dimethylformamide), DMAc (dimethylacetamide), butyl cellosolve acetate and N-methyl-2-pyrrolidone is rotationally applied on to the substrate, the solvent is evaporated to form the coating film. The polyimide film thus produced has the following problems, however.
(1) In the process using the polyamic acid of precursor, the baking at high temperature of 250xc2x0 C. or more is needed for imidization of the polyamic acid. Also, in the process using polyimide itself as well, since there is no proper low-boiling-point solvent for dissolving the polyimide, rather high temperature is required for removal of the solvent. As mentioned above, the organic solvents that may be used for dissolving the polyimide include, for example, DMF, DMAc, butyl cellosolve acetate and N-methyl-2-pyrrolidone. However, these solvents are all high in boiling point (153xc2x0 C., 165xc2x0 C., 192xc2x0 C. and 202xc2x0 C., respectively) and also are flammable, so that when the film is formed, these solvents must be evaporated and dried at high temperature, while taking explosion-protection into consideration. In the circumstances, a special device for the heating is additionally needed for forming the polyimide film and accordingly the manufacturing costs increase. Also, there is the possibility that e.g. TFT circuits may be damaged by heating.
(2) Since the polyimide is not adequate to form the film, it is hard for the polyimide to produce a coating film of thin and uniform film thickness. Due to this, display unevenness originating from unevenness of the film thickness is generated. Also, since a thick coating film serves as the insulating film, it is hard to realize the liquid crystal display of low voltage drive.
When the polyimide film involving the various problems mentioned above is used as the liquid crystal alignment film and is subjected to the alignment process such as the rubbing process, additional problems are further caused as follows.
{circle around (1)} When the coating film has projections and depressions, it cannot be rubbed at its depressed part. The coating film particularly for a larger area panel would not be rubbed uniformly, so that the problems, such as deficiency in alignment, display unevenness and display burn-in, are caused.
{circle around (2)} Static electricity is generated on the alignment film, and as such can cause a possible lowering of the TFT function.
{circle around (3)} Further, dust is produced from rubbing material (cotton cloth and the like), and the dust accounts for variations of display unevenness and the gap between the substrates.
These problems become outstanding particularly in the following cases. For example, Japanese Laid-open (unexamined) Patent Publication No. Hei 5-173,135 proposes the method wherein the process that the alignment film is rubbed in a certain direction and further is rubbed in the opposite direction after the concerned part is covered with resist is repeated a given number of times to form a number of areas varied in orientation of alignment of liquid crystal. This method produces the effect in providing a modified viewing angel characteristic to the TN mode of liquid crystal display element having its inherent disadvantage of narrow viewing angle. However, the complicated work that the masking is done for each of divided regions in advance of the rubbing must be repeated, in order to form a number of divided areas varied in orientation of alignment of liquid crystal. This causes the production efficiency of the alignment film to be lowered to a large extent and also causes the dust generation problem into further serious problem.
Under the circumstances, various non-contact alignment modes have been proposed with the aim of solving the problems involved in the rubbing mode.
For example, Japanese Laid-open (unexamined) Patent Publication No. Hei 5-53,118 proposes the technique that a photosensitive composition layer is formed on the substrate and then grooves in specific patterns are formed on the composition layer through the exposure and heating processes, so that the alignment of liquid crystal is provided by the grooves thus formed. However, this technique requires large light energy for forming the grooves. Further, it is difficult for the grooves to be formed uniformly, thus causing the problems of display unevenness and the like. Furthermore, it has the problem that the control of the alignment of the liquid crystal is not sufficient.
Japanese Laid-open (unexamined) Patent Publication No. Hei 7-72,483 proposes the technique that the alignment film forming compound layer including polyimide or precursor of polyimide is directly irradiated with polarized light to polymerize the polyimide and the like, so as to provide the alignment of liquid crystal. However, since this technique uses the polyimide of organic polymer, if the alignment film has large thickness, the problem of increased liquid crystal driving voltage cannot be solved. Further, the technique has an additional problem that anchoring strength of the alignment film to the substrate is insufficient.
Japanese Laid-open (unexamined) Patent Publication No. Hei 7-318,942 proposes the technique that the alignment film having the polymer structure is obliquely irradiated with light to cause additional bond or decomposing reaction of molecular chains of the alignment film to thereby produce the molecular structure having the alignment of liquid crystal. However, this technique is intended for the alignment film comprising organic polymer, such as polyimide, polyvinyl alcohol and polystyrene. Accordingly, this technique cannot dissolve the above-noted problems of the large film thickness, the small anchoring strength of the alignment film for the substrate, and others, either. Also, it is essential for this technique that the alignment film for which a pretilt angle is given is irradiated with light from an oblique direction. However, in order for the alignment film to be accurately irradiated with light from such an oblique direction, a high-precision light irradiation device is required and accordingly the production costs increase to that extent.
Applications of the techniques described by the publications as noted above could form a number of divided areas varied in orientation of alignment of liquid crystal and accordingly could also apply to the TN mode of liquid crystal display element having a narrow viewing angle. However, since the respective techniques have the problems of the large film thickness, the small anchoring strength of the alignment film for the substrate, and others, as mentioned above, the applications thereof could not provide a fully satisfactory liquid crystal alignment film, after all.
One the other hand, a VA (vertical alignment) mode of liquid crystal display capable of realizing high contrast and high-speed response have begun to make a mark in recent years. In this alignment mode, the vertical alignment of liquid crystal molecules can be realized by use of a VA-use liquid crystal alignment film. The VA-use liquid crystal alignment films include the one formed by the polyimide, in which a long-chain alkyl group or a fluoric functional group is introduced into the side chain, being used as the alignment film material. However, such alignment film material is, in general, high in surface energy (e.g. low in water repellency), thus suffering the problem of being inferior in adhesion to the substrate. In addition, since the alignment film is formed of polymer, it is large and uneven in thickness and thus has insulative property, thus suffering the aforementioned problem that transmission of light and electric field to drive the liquid crystal molecules are hindered. Further, although the action of the side chain is the factor contributing to the vertical alignment of the liquid crystal molecules, it is impossible to make the control of allowing the side chain to be efficiently exposed on the boundary between the side chain and the liquid crystal. For this reason, the part of the alignment film to contribute to the alignment of the liquid crystal molecules is apparently low in density, as compared with the monomolecular film, thus suffering the difficulties of adequate control of alignment of liquid crystals.
Meanwhile, in Japanese Laid-open (unexamined) Patent Publication No. Hei 3-7,913 the inventors previously proposed the technique for producing the alignment film having thickness of a level of nanometer with efficiency. This technique uses the monomolecular layer, which is formed by silane-baced chemical adsorption material (which is also called the surface-active agent) being chemically adsorbed on the substrate as the alignment film. This technique can produce the result that a very thin transparent coating film bonded and anchored on the substrate can be formed with ease and efficiency. Besides, it can provide the alignment film having some capability of controlling alignment of liquid crystal molecules without any rubbing process. This technique still has room for improvement on the thermal stability of the alignment and the controllability of the alignment, however.
In consideration of the present situation mentioned above, a group of inventions have been made. It is the primary object of the invention to provide a novel, thin-film forming, chemical adsorption material which is capable of forming a thin-film of a monomolecular layer form and has a photosensitive group which is transparent and stable in a visible light region and causes photochemical reaction in a ultraviolet light region and also provide the producing method thereof.
It is the secondary object of the invention to provide a novel, vertical alignment-use, liquid crystal alignment film having a very small thickness of a level of nanometer that can be uniformly and strongly anchored on the substrate, is excellent in thermal stability and controllability of alignment and wide in viewing angle, capable of high-response and high-contrast control of alignment via the vertical alignment, and can be produced with good productivity and to provide a novel liquid crystal display element using such a liquid crystal alignment film.
Although the group of inventions is based on the same or similar conception, since they are realized by way of different examples, the inventive groups are divided into the first inventive group, the second inventive group and the third inventive group on the basis of their respective relevance. In the following, the contents will be explained in order for each division (each inventive group).
The inventors of this application have discovered that chemical adsorption material having a chalcone skeleton can be chemical adsorbed on the base substance to form a transparent coating film of a monomolecular layer form and also it has reactivity to light in a far ultravioletxc2x7ultraviolet light (of wavelength of 200 nm to 400 nm) region, while on the other hand, it exhibits stability to light in a visible light (of wavelength of 400 nm to 700 nm) region, and further have made an analysis thereon. As a result of the study, they have completed a novel, thin-film forming, chemical adsorption material (hereinafter it sometimes simply referred to as a chemical adsorption material) and a producing method of this chemical adsorption material. 
In order to attain the primary object mentioned above, an organic thin film according to the first inventive group comprises at least a functional group expressed by the following chemical formula (1-1) and a xe2x80x94SiX group (X represents halogen) as an end group bonded by siloxane bond:
The functional group expressed by the chemical formula (1-1) includes the chalcone skeleton expressed by the following chemical formula (1-4), so that when the functional group is irradiated with light in the ultraviolet light region, it functions as a photosensitive group and permits the molecules to be cross-linked to each other. 
Further, since a perfluoromethyl group (xe2x80x94CF3 group) represented in the chemical formula (1-1) has the minimum critical surface tension of all atoms and groups, so it has the property of repelling the liquid crystals. Also, according to the thin film forming chemical adsorption material having the above-noted constitution, since there is included a SiX group as an end group bonded by the siloxane bond, the Si portion functions as the chemical adsorption group and is allowed to react with a functional group existing on the surface of the base substance to be chemically adsorbed thereon.
The compound expressed by the following chemical formula (1-2) is preferably used as the chemical adsorption material. 
The thin film forming chemical adsorption material having these properties is useful as a functional coating film material for modifying the property of the surface of the base substance, particularly as a liquid crystal alignment film material. For example, when the thin film forming chemical adsorption material is used as the liquid crystal alignment film material, the following operation and effect are provided. The thin film formed by putting the chemical adsorption material into contact with the base substance so as to be chemically adsorbed thereon has the structure of a monomolecular layer form in which molecules are arranged laterally, with their one long axial ends (SiX groups) being bonded to the surface of the base substance and the other ends being oriented to a direction for them to be away from the base substance. This coating film is of very thin of a level of nanometer and is chemically stable and transparent in the visible light region.
On the other hand, since the chemical adsorption material has the properties that a vinyl group portion causes a light reaction by the irradiation of light in the ultraviolet light region, when the chemical adsorption material as was chemically adsorbed on the base substance is irradiated with ultraviolet light, the adsorption molecules is cross-linked to each other. This can provide the liquid crystal alignment film in which the alignment of the adsorption molecules are strically stabilized. Also, when polarized light is used in the irradiation of ultraviolet light, a cross-link reaction can be caused along a specific direction. Accordingly, when the polarizing direction is regulated, the orientation for the adsorption molecules to be aligned can be controlled.
It is to be noted here that with the thin film of a monomolecular layer form having the structure that the chemical adsorption material is adsorbed along the base substance, it is possible for the liquid crystal molecules to enter the spaces (valleys) between the individual adsorption molecules. Consequently, the thin film in which thin film constituent molecules (adsorption molecules) are aligned in a given direction has a specific orientation of liquid crystals. With this thin film, since the constituent molecules of the thin film are each contributive to the orientation of liquid crystals, although the film is a very thin coating film of a monomolecular layer form, it exerts strong control of alignment of liquid crystals. Further, since the end group of the thin film constituent molecule on the front side of the thin film is a perfluoromethyl group having a very small critical surface tension, the liquid crystal molecules can be aligned at a high pretilt angle. Also, since the adsorption molecules are linked and bonded to each other by the cross-link reaction, the alignment properties are prevented from being deteriorated due to external factors such as heat and friction.
In addition, since this coating film is very thin and transparent and also is not an organic polymer film, it hardly serves as an electric resistance film. Consequently, it has significantly advantageous properties as the liquid crystal alignment film that it does not hinder the transmission of light and the electric field to drive the liquid crystals.
In contrast to this, in the conventional liquid crystal alignment film (e.g. a polymer film made of polyimide) in which the long chains are densely and irregularly complicated, only a surface part thereof is contributive to the alignment of the liquid crystals, so that it is hard to obtain adequate controllability of the alignment of the liquid crystals. In the conventional alignment film having the alignment property given by the rubbing, the alignment property is varied or deteriorated by external factors such as heat and friction. Further, since the polymer film made, for example, of polyimide is large in thickness and high in electric resistance, it provides inhibition factors to hinder the transmission of light and the electric field to drive the liquid crystals.
The chemical adsorption material of the present invention can be produced by a producing method comprising at least:
the chemical reaction process 1 that at least 4-(2,2,3,3,3-Pentafluoropropyloxy) benzaldehyde and 4-Hydroxyacetophenone are subjected to aldol condensation reaction to synthesize alcohol having a chalcone skeleton expressed by the following chemical formula (1-3) (chemical reaction process 1); and the chemical reaction process 2 that after the chemical reaction process 1, SiX4 (X represents halogen) is subjected to dehydrohalogenation reaction with alcohol having the chalcone skeleton under an inert gas atmosphere, to synthesize chemical adsorption material having a characteristic group expressed by the following chemical formula (1-1) and a xe2x80x94Oxe2x80x94SiX3 group: 
This can produce the chemical adsorption material that can permit the molecules to be cross-linked with each other and also allow them to react with the surface functional group existing on the surface of the base substance so as to be chemically adsorbed thereon when irradiated with the light in the ultraviolet light region.
Further, the chemical adsorption material include a compound expressed by the following chemical formula (1-2): 
In order to attain the secondary object mentioned above, an organic thin film according to the secondary inventive group comprises an aggregation of adsorption molecules directly bonded and anchored to or indirectly bonded and anchored to a surface of a base substance through another material layer, wherein the adsorption molecules have a characteristic group expressed by the following chemical formula (1-2) and a xe2x80x94Oxe2x80x94Si bond group at a molecular end group: 
The organic thin film having the constituent mentioned above comprises the aggregation of adsorption molecules arrayed along the surface of the base substance in the state in which they are chemically adsorbed on the base substance at one end thereof (on the xe2x80x94Oxe2x80x94Si bond group side) and are projected out from the surface of the base substrate in a direction of being away therefrom. In the aggregation of adsorption molecules comprising the characteristic group expressed by the chemical formula (2-1) and the xe2x80x94Oxe2x80x94Si bond group, since the individual adsorption molecules are strongly bonded and anchored to the substrate via the chemical bonding, the peeling of the coating film is prevented. Consequently, it has an excellent anti-peeling property.
When this organic thin film is applied to the liquid crystal alignment film, the liquid crystal molecules can enter the spaces (valleys) between the adsorption molecules in the aggregation of adsorption molecules and are then controlled to the tilt and/or orientation of alignment of the liquid crystals with respect to the substrate (hereinafter it is collectively called the alignment direction). Consequently, although the film is a very thin coating film of a monomolecular layer form, it exerts strong control of alignment of liquid crystals. Further, since it has a perfluoromethyl group (xe2x80x94CF3 group) having a very small critical surface tension as the end group of the thin film constituent molecule on the front side of the thin film, the liquid crystal molecules can be aligned at a high pretilt angle. Also, since the liquid crystals can strongly be bonded to the substrate through Si atoms and also the adsorption molecules can strongly be bonded to each other through Si, the liquid crystal alignment film of excellent durability can be obtained.
The base substances that may be used include, for example, a substrate made of glass and the like and those made of metal, ceramics, glass, plastics, polymer, paper, fiber and leather. Further, electrodes (including wires) and/or other material layers may be formed on the substrate.
The adsorption molecules forming the organic thin film may be molecules in which the chalcone skeleton of the functional group shown in the chemical formula (2-1) and xe2x80x94Oxe2x80x94SiX group are directly bonded to each other or the functional groups cited below as an example are indirectly bonded to the chalcone skeleton via the xe2x80x94Oxe2x80x94 bond.
(1) Hydrocarbon radicals such as xe2x80x94(CH2)n (where n is an integer number of 1-20) and xe2x80x94C6H5;
(2) Hydrocarbon radicals of the carbon-carbon double bond or the carbon-carbon triple bond being included in a part of the hydrocarbon radicals as listed in the above item (1) (except xe2x80x94CH2);
(3) Functional groups of which hydrogen of hydrocarbon radicals of the items (1) and (2) above is replaced with other functional group (e.g. a methyl group, a halogenated methyl group, a hydroxyl group, a cyano group, etc.) and/or atoms (e.g. F, Cl, Br, I, etc.); and
(4) Functional groups in which the Cxe2x80x94C bond of hydrocarbon radicals of the above items (1) and (2) is partly replaced with the Cxe2x80x94Oxe2x80x94C (ether) bond or the Cxe2x80x94COxe2x80x94Cxe2x80x94(carbonyl) bond.
The absorption molecules explained above include those having the chemical constituent expressed, for example, by the following chemical formula (2-2): 
The aggregation of adsorption molecules is permitted to be aligned in a given direction. When the organic thin film is used as the liquid crystal alignment film, this can provide a uniform liquid crystal alignment property to the liquid crystal alignment film.
In this constituent, the adsorption molecules in adjoining divided regions may be differentiated from each other in tilt of their major exes with respect to the surface of the substrate and/or in orientation of alignment thereof. The divided regions means the regions formed by dividing a single picture element into a number of regions in a pattern-like form. When the film is formed as the so-called, multi-domain type liquid crystal alignment film in which the alignment direction of the adsorption molecules are controlled in each of the minute regions into which the one picture element is divided in a pattern, the light transmitting in each picture element is formed by a number of bundles of rays different in angle from each other. Thus, the dependency of the display on the viewing angle is reduced.
In the constituent above, the adsorption molecules of the aggregation of adsorption molecules may be cross-linked to each other via a boning line(s) of Cxe2x80x2 and/or Cxe2x80x3 in the chemical formula (2-1) or (2-2). Since the adsorption molecules are strongly anchored to each other via the cross-link bond, the tilt and the alignment direction of the adsorption molecules are prevented from being varied by external factors such as friction and heat. Consequently, the organic thin film having high reliability can be obtained.
In the constituent above, the organic thin film may have film thickness of 0.5 nm or more to less than 10 nm. With the film thickness of this range, the efficiency of alignment is high in the relation with the film thickness and also the transmission of light and the electric field are not unnecessarily hindered. Consequently, when the organic film is applied to the liquid crystal alignment film, the usability is further improved.
In the constituent above, the organic thin film may be formed by a thin film of a monomolecular layer form. The thin film of a monomolecular layer form can provide the result that when applied to the liquid crystal alignment film, the individual adsorption molecules are directly contributive to the alignment of the liquid crystal molecules. Thus, the liquid crystal alignment efficiency is considerably improved in the relation with the film thickness.
In the constituent above, the organic thin film may comprise an aggregation of adsorption molecules of various kinds. The organic thin film comprising the aggregation of adsorption molecules of various kinds can produce the organic thin film having multifunction.
When the organic thin firm is applied to the liquid crystal alignment film, that liquid crystal alignment film can become an alignment film that develops a desired pretilt angle for the liquid crystal molecules.
In the constituent above, the liquid crystal alignment film may comprises the aggregation of adsorption molecules of various kinds, and the liquid crystal molecules may be aligned at a desired pretilt angle by changing a constituent ratio between the various kinds of adsorption molecules.
It is to be noted here that in addition to the adsorption molecules having a characteristic group expressed by the chemical formula (2-1) and a xe2x80x94Oxe2x80x94Si bond group at a molecular end group, the adsorption molecules that may be used include, for example, adsorption molecule having a xe2x80x94Oxe2x80x94Si group and a long chain alkyl group (number of carbon: 7 or more to 18 or less) and adsorption molecule having a xe2x80x94Oxe2x80x94Si bond group and a long chain fluorocarbon group (number of carbon: 7 or more to 18 or less). In addition, the adsorption molecule in which a cyano group, an ester group, a chloro group or a bromo group is bonded to an end of the alkyl group and fluorocarbon group can also be cited. Further, these adsorption molecules may be adsorption molecules having a characteristic group expressed by the chemical formula (2-1).
Next, the producing method of the organic thin film of the present invention will be described. The inventive producing method of an organic thin film comprising an aggregation of adsorption molecules directly bonded and anchored to or indirectly bonded and anchored to a surface of a base substance through another material layer via chemical adsorption, the producing method comprising: the process that chemical adsorption material having a characteristic group expressed by the following chemical formula (2-1) and a xe2x80x94Oxe2x80x94Si bond group at a molecular end portion thereof is at least dissolved in non-water-borne solvent, to prepare chemical adsorption solution: the process that the chemical adsorption solution is put into contact with the surface of the base substance, so that the chemical adsorption material in the chemical adsorption solution is chemically adsorbed on the surface of the base substrate; and the solution draining and drying process that the surface of the base substance to which the chemical adsorption material was bonded is cleaned by use of the non-water-borne solvent and, thereafter, the base substance is stood up in a specific direction to cut and dry the cleaning solution: 
The producing method above may further comprises the polarized ultraviolet irradiation process that after the solution draining and drying process, the adsorption molecules on the surface of the base substance are irradiated with polarized ultraviolet light, so that they are cross-linked to each other via a bonding line of a carbon-carbon double bond portion of the chemical formula (2-1).
The producing method above may be so constituted that a series of alignment film treatment processes comprising the solution draining and the drying process and a polarized ultraviolet irradiation process are repeated a number of times in such a manner that the solution draining and drying process returns back again from the polarized ultraviolet irradiation process, and each time when repeated, the solution draining and drying direction is varied and that the polarized ultraviolet light irradiation region and polarized ultraviolet light irradiation direction, or the polarized ultraviolet light irradiation region and polarized ultraviolet light irradiation angle, or the polarized ultraviolet light irradiation region, polarized ultraviolet light irradiation direction and polarized ultraviolet light irradiation angle, are varied, whereby the adsorption molecules are varied in tilt of their major exes with respect to the surface of the base substance and/or in orientation of alignment thereof from one divided region to another of a number of divided regions into which a region corresponding to one picture element is divided in a pattern-like form. This constitution enables the organic thin film suitable for the multi-domain alignment to be produced reliably and with improved productivity.
In the producing method, aprotic solvent may be used as the non-water-borne solvent for use in cleaning so that the unreacted chemical adsorption material can be cleaned and removed from the surface of the base substance by use of the aprotic solvent, to produce a thin film of a monomolecular layer form.
Alternatively, a mixed solvent of aprotic solvent and protic solvent may be used as the non-water-borne solvent for use in cleaning, so that unreacted chemical adsorption material can be cleaned and removed from the surface of the base substance by use of the mixed solvent, to produce a thin film of a monomolecular layer form. The use of the mixed solvent is of desirable in that the chemical adsorption material dissolving capability and evaporation speed can be adequately adjusted.
The significance of the constitutions above will be described. When the solution of the chemical adsorption material having the characteristic group expressed by the chemical formula (2-1) and the xe2x80x94Oxe2x80x94Si bond group at a molecular end portion thereof is put into contact with the substrate, the chemical adsorption material is allowed by react with the surface functional group having active hydrogen on the surface of the substrate to be chemically adsorbed thereon, so as to form an organic thin film. The organic thin film comprises the aggregation of adsorption molecules whose one long axial ends (xe2x80x94Oxe2x80x94Si bond group) are bonded to the surface of the base substance and whose other ends are oriented to a direction for them to be away from the base substance. When this organic thin film comprising the aggregation of adsorption molecules is applied to the liquid crystal alignment film, the liquid crystal molecules can enter the spaces (valleys) between the adsorption molecules and are then controlled to the alignment direction of the liquid crystal molecules with respect to the substrate. Consequently, the alignment direction of the liquid crystal molecules can be controlled by regulating the alignment direction of the adsorption molecules.
On the other hand, the compound having the characteristic group expressed by the chemical formula (2-1) has the properties that it is transparent and chemically stable in the visible light region and also high in sensitivity to ultraviolet light at the carbon-carbon double bond portion thereof. Consequently, when the adsorption molecules are chemically adsorbed on the substrate and then are irradiated with ultraviolet light, they can be cross-linked to each other through the carbon-carbon double bonding. In this process, when the polarized ultraviolet light is used, the cross-link direction can be controlled to a specific direction corresponding to the polarizing direction of the polarized light. Then, the adsorption molecules on the surface of the substrate are re-aligned by the irradiation of the polarized light and the re-alignment is provided by the molecules being cross-linked to each other, and as such can produce the resistance to the external factors such as heat and friction.
The chemical adsorption material having the characteristic group expressed by the chemical formula (2-1) and the xe2x80x94Oxe2x80x94Si bond group at a molecular end portion thereof that may be used include a compound expressed by the following chemical formula (2-2). 
The chemical adsorption material expressed by the chemical formula (2-2) can be chemically adsorbed on the surface of the base substance with ease. Also, the material is strong in bond and high in light-sensitivity at the carbon-carbon double bond portion thereof. In addition, since this material has a perfluoromethyl group at the end group thereof on the front side of the film, it can permit the liquid crystal molecules to be aligned at a high pretilt angle. From the foregoing, the producing method using the compound of chemical formula (2-2) can produce the organic thin film suitably used as the liquid crystal alignment film with improved productivity.
The principal part of the producing method will further be explained. In the solution draining and drying process according to the producing method of the present invention, non-adsorbed chemical adsorption material existing in surplus on the surface of the substrate is first removed by the cleaning process and then the non-water-borne cleaning solvent is dried and removed in the solution draining and drying process. Through this series of operations, the thin film of a monomolecular layer form in which the adsorption molecules are aligned in the solution draining and drying direction can be formed on the substrate. However, this alignment of the adsorption molecules provided by a solution draining and drying process is varied by another solution draining and drying process and is subjected to change by external factors (e.g. heat and friction). Accordingly, this alignment is referred to as xe2x80x9cthe tentative alignmentxe2x80x9d in this specification.
Further, in the polarized ultraviolet light irradiation process, the surface of the thin film subjected to the tentative alignment (the aggregation of adsorption molecules) is irradiated with polarized ultraviolet light. The adsorption molecules having the characteristic group expressed by the chemical formula (2-1) have high light-sensitivity. Consequently, the adsorption molecules are allowed to react with each other at the carbon-carbon double bonding portion by the irradiation of polarized ultraviolet light and are cross-linked in a specific direction corresponding to the polarizing direction through the bonding line of the carbon. It is to be noted that the polarizing direction may be identical with the tentative alignment direction or different from it. In either case, the adsorption molecules can be re-aligned in a specific direction corresponding to the polarizing direction by the irradiation of polarized light. However, the solution draining direction and the polarizing direction should not be crossed exactly at 90 degree, but should be somewhat, or preferably some degrees or more, out of position therefrom. This is because, if they are crossed exactly at 90 degree, there is the possibility that the individual molecules could be oriented in two random directions.
The reason therefor has not yet fully clarified, but it was experimentally confirmed that when the thin film, after tentatively aligned, was irradiated with polarized ultraviolet light, the cross link proceeded in a specific direction smoothly to provide an improved alignment treatment effect by the polarized ultraviolet light.
In this specification, in order to differ from the tentative alignment, the alignment performed via the irradiation of the polarized ultraviolet light is called xe2x80x9cthe re-alignmentxe2x80x9d. Further, the molecules as were chemically adsorbed on the substrate are called xe2x80x9cchemical adsorption materialxe2x80x9d. Further, it was experimentally confirmed that the thin film formed by the adsorption molecules being chemically adsorbed on the substrate had thickness of a level generally equal to molecular length of the adsorption molecules (a level of nanometer).
In this connection, the difference between the organic thin film as the liquid crystal alignment film according to the present invention and the conventional liquid crystal alignment film is as follows. In the conventional liquid crystal alignment film (e.g. a polymer film made of polyimide) in which the long chains are densely and irregularly complicated, only a surface part thereof is contributive to the alignment of the liquid crystals, so that it is hard to obtain adequate controllability of the alignment of the liquid crystals. In addition, in the conventional alignment film having the alignment property given by the rubbing, the alignment property is varied or deteriorated by external factors such as heat and friction. Further, since the polymer film made, for example, of polyimide is large in thickness and high in electric resistance, it provides inhibition factors to hinder the transmission of light and the electric field to drive the liquid crystals.
On the other hand, even the liquid crystal alignment film comprising the thin film of a monomolecular layer form is insufficient in alignment stability, if it is the alignment film wherein the adsorption molecules are not cross-linked to each other. For example, the chemical adsorption material described in the above-mentioned Japanese Laid-open (unexamined Patent Publication No. Hei 3-7,913 has no photosensitive group, as such cannot allow the adsorption molecules to be chemically bonded to each other. The liquid crystal alignment film made by using this material has the disadvantage that when it is heated around 200xc2x0 C., the alignment property deteriorates easily.
Next, description will be given on the liquid crystal display of the present invention using the above-mentioned organic thin film as the liquid crystal alignment film. The liquid crystal display of the present invention comprising a pair of opposed substrates; a liquid crystal alignment film formed at least on a surface of a substrate having electrodes of the pair of substrates; and liquid crystals accommodated in a cell gap between the pair of opposed substrates, wherein the liquid crystal alignment film comprises an aggregation of adsorption molecules bonded and anchored directly on a surface of the substrate forming the electrodes thereon or indirectly bonded and anchored thereon through another material layer via chemical adsorption, and wherein the aggregation of adsorption molecules include adsorption molecule having a characteristic group expressed by the following chemical formula (2-1) and a xe2x80x94Oxe2x80x94Si bond group at a molecular end group: 
In the above constitution, a pretilt angle and/or a pretilt orientation of the adsorption molecules accommodated in the cell gap are controlled by tilt and/or orientation of alignment of the adsorption molecules"" major axes with respect to surface of the substrate.
In the liquid crystal display thus constructed, the adsorption molecules may be differentiated from each other in tilt and/or orientation of alignment of their major axes with respect to the surface of the substrate from one divided region to another of adjoining divided regions into which a single picture element is divided in a pattern-like form.
An in-plane switching type liquid crystal display of the present invention comprises pixel electrodes and opposed electrodes, which are arranged on a substrate, and a liquid crystal alignment film formed on a surface of the substrate on which the electrode are arranged, wherein the liquid crystal alignment film comprises an aggregation of adsorption molecules bonded and anchored directly on a surface of the substrate forming the electrodes thereon or indirectly bonded and anchored thereon through another material layer via chemical adsorption, and wherein the aggregation of adsorption molecules include adsorption molecule having a characteristic group expressed by the following chemical formula (2-1) and a xe2x80x94Oxe2x80x94Si bond group at a molecule end group: 
In the liquid crystal display (including the in-plane switching type one, same applies to the following), a pretilt angle and/or a pretilt orientation of the adsorption molecules accommodated in the cell gap are be controlled by tilt and/or orientation of alignment of the adsorption molecules"" major axes with respect to the surface of the substrate.
The adsorption molecules forming the liquid crystal alignment film may be cross-linked to each other via a boning line(s) of Cxe2x80x2 and/or Cxe2x80x3 in the chemical formula (2-1) or (2-2).
The adsorption molecule having the characteristic group expressed by the chemical formula (2-1) and the xe2x80x94Oxe2x80x94Si bond group may have the structure shown in the following chemical formula (2-2). 
The liquid crystal alignment film preferably has film thickness of 0.5 nm or more to less than 10 nm.
The liquid crystal alignment film may preferably be a thin film of a monomolecular layer form. The liquid crystal alignment film of a monomolecular layer form can provide a considerably reduced degree of hindrance of the electric field to drive the liquid crystals and also can prevent hindering the transmission of light even when it is arranged in a light transmission path. Consequently, the liquid crystal display that can be driven at low voltage and is excellent in brightness can be realized.
Incidentally, an ideal monomolecular layer means a layer in which individual constituent molecules are arranged along the surface of the substrate without overlapping with each other, but realistically it is not easy to form such a complete monomolecular layer. Even when the monomolecular layer is not complete, the object of the present invention can be fully achieved. Accordingly, the termination of xe2x80x9cthin film of a monomolecular layer formxe2x80x9d used in the specification is intended to cover any thin film of a level of thin film that can be considered as a generally monomolecular layer. For example, the thin film of a monomolecular layer form of the present invention covers a thin film having at a part thereof a multi-molecular layer formed by non-adsorbed molecules being laid on the adsorption molecules adsorbed on the substrate; and a layer formed by a number of molecules that are continuously bonded in such a form that the molecules that are not directly bonded and anchored to the substrate by themselves are bonded to the molecules directly bonded thereto and further other molecules are bonded to the molecules that are not directly bonded thereto.
While the description above is given on the condition that an aggregation of adsorption molecules are composed of only one chemical adsorption material, other adsorption material may be mixed in the adsorption molecules according to the present invention.
Next, the producing methods of the liquid crystal display of the present invention will be described. The present invention provides a producing method of a liquid crystal display having a liquid crystal alignment film comprising an aggregation of adsorption molecules directly bonded and anchored to or indirectly bonded and anchored to a surface of a substrate forming thereon electrodes through another material layer via chemical adsorption, the producing method comprising: the process that chemical adsorption material having a characteristic group expressed by the following chemical formula (2-1) and a xe2x80x94Oxe2x80x94Si bond group at a molecular end portion thereof is dissolved in non-water-borne solvent, to prepare chemical adsorption solution: the process that the chemical adsorption solution is put into contact with the surface of the substrate forming the electrodes thereon, so that the chemical adsorption material in the chemical adsorption solution is chemically adsorbed on the surface of the substrate; and the solution draining and drying process that the surface of the substrate to which the chemical adsorption was bonded is cleaned by use of the non-water-borne cleaning solvent and, thereafter, the substrate is stood up in a specific direction to cut and dry the cleaning solution: 
The producing method above may further comprises the polarized ultraviolet irradiation process that after the solution draining and drying process, the adsorption molecules on the surface of the substrate are irradiated with polarized ultraviolet light, so that they are cross-lined to each other via a bonding line of a carbonxe2x80x94carbon double bond portion of the chemical formula (2-1).
In the producing method above, a series of alignment film treatment processes comprising the solution draining and the drying process and the polarized ultraviolet irradiation process are repeated a number of times in such a manner that the solution draining and drying process returns back again from the polarized ultraviolet irradiation process; and each time when repeated, the solution draining and drying direction is varied and that the polarized ultraviolet light irradiation region and polarized ultraviolet light irradiation direction, or the polarized ultraviolet light irradiation region and polarized ultraviolet light irradiation angle, or the polarized ultraviolet light irradiation region, polarized ultraviolet light irradiation direction and polarized ultraviolet light irradiation angle, are varied, whereby the adsorption molecules are varied in tilt of their major exes with respect to the surface of the substrate and/or in orientation of alignment thereof from one divided region to another of a number of divided regions into which a region corresponding to one picture element is divided in a pattern-like form. This method can reliably and efficiently produce the liquid crystal display having the multi-domain type liquid crystal alignment film which is varied in alignment direction from one divided region to another of the divided regions divided in a pattern-like form.
Aprotic solvent may be used as the non-water-borne solvent for use in cleaning, so that unreached chemical adsorption material is cleaned and removed from the surface of the substrate by use of the aprotic solvent, to produce a thin film of a monomolecular layer form.
Also, a mixed solvent of aprotic solvent and protic solvent may be used as the non-water-borne solvent for use in cleaning, so that unreacted chemical adsorption material is cleaned and removed from the surface of the substrate by use of the mixed solvent, to produce a thin film of a monomolecular layer form.
The chemical adsorption material having a characteristic group expressed by the chemical formula (2-1) and a xe2x80x94Oxe2x80x94Si bond group at a molecular end portion thereof may be a compound expressed by the following chemical formula (2-2). 
These and other objects, features and advantages of the present invention will fully be understood by reference to the following description. Also, the merits of the present invention will become more apparent upon reading the following description referring to the accompanying drawings.